Meanwhile, a new cabinet is expected to be presented to protesters in Kiev on Wednesday afternoon.

Analysis

By David SternBBC News, Kiev

Ukraine's new leaders are tasked with not just forming a new government, but also stabilizing the country, finding the fugitive former President Viktor Yanukovych, and staving off a looking financial catastrophe. They must also transform the basic way the country is governed and its economy is run.

In order to unlock billions of dollars in emergency loans from the International Monetary Fund, interim officials must agree to reforms in key areas such as the gas and agriculture industries. They must also overhaul the country's judiciary, where, in the words of one expert, Adrian Karatnycky of the Atlantic Council, court decisions were decided by "a phone call from the presidential administration."

And there are many more areas. All them carry heavy political and economic risks, and could spark a backlash from interested or affected groups - for instance, the Berkut themselves. Or Ukrainians forced to pay higher gas prices. Or the industry tycoons, who will see their revenues diminish. But not doing anything will also unleash a reaction - especially from the still-present protestors on the Maidan. The government can't afford not to act.

Also on Wednesday Mr Turchynov announced that he had assumed the duties of the head of the armed forces.

Ousted President Viktor Yanukovych fled Kiev at the weekend and his whereabouts are still unknown.

Interim authorities have issued a warrant for his arrest, and on Tuesday parliament voted in favour of trying him at the International Criminal Court (ICC) in The Hague.

The fugitive president is accused of being behind the deaths of more than 100 protesters at the hands of riot police.

Any new government will face a daunting set of challenges, with many areas of government in Ukraine needing urgent reform, the BBC's David Stern in Kiev reports.

The much-despised Berkut are just one part of the security and law enforcement agencies, which have long been accused by human rights groups and local citizens of human rights abuses.

International divisions

Also on Wednesday Russian Foreign Minister Sergei Lavrov called on other countries to condemn "nationalist and neo-fascist" sentiment in western Ukraine.

Mr Lavrov called on the OSCE to condemn "calls to ban the Russian language, to turn the Russian-speaking population into 'non-citizens' and to restrict freedom of expression".

Images of some those killed in recent violence can be seen in a memorial in Kiev's Independence Square

The square has become a shrine to the dead

However, many who favour closer ties with Russia have been unhappy at the turn of events in Kiev

The BBC's Steve Rosenberg tweeted this picture of documents fished out of a lake at Mr Yanukovych's residence, now being dried out in a sauna at the property

Russia has portrayed the ousting of Mr Yanukovych as a violent seizure of power by the opposition, and has expressed concern about the role of far-right parties in the protests against him.

The US and EU countries have broadly backed the takeover of power by the opposition.

Many Russian-speaking residents in the south and east of Ukraine have protested against the actions of the interim authorities.

Tensions are rising in Crimea, where two big rival protests are being staged.

Crimean Tatars and local activists supporting the demonstrators in Kiev have gathered in front of the autonomous republic's parliament in Simferopol.

They are facing a pro-Russian demonstration, with only a police cordon separating the two rallies.

The Crimean Tatars say they will resist any attempts at secession by pro-Russian political forces.

The two rival rallies have been called ahead of a planned session of Crimea's parliament, where the issue of Crimea's status is expected to be raised.

Crimea - where ethnic Russians are in a majority - was transferred from Russia to Ukraine in 1954.

The change of government in Kiev has raised questions over the future of Russia's naval bases in the Crimean port city of Sevastopol, the lease for which was extended until 2042 by Mr Yanukovych.

Most experts believe that the new leadership will not push for the withdrawal of the Russian fleet, as this could further threaten Ukraine's internal stability as well as the country's fragile relations with Russia, the BBC's Ilya Abishev reports.

Earlier, Ukraine's Mr Turchynov expressed concern about what he called the serious threat of separatism following the ousting of Mr Yanukovych.

Addressing parliament, he said he would meet law enforcement agencies to discuss the risk of separatism in regions with large ethnic Russian populations. Separatism was a "serious threat", he said.

Fugitive president

Mr Yanukovych fled Kiev at the weekend and his whereabouts are still unknown.

Interim authorities have issued a warrant for his arrest, and on Tuesday parliament voted in favour of trying him at the International Criminal Court (ICC) in The Hague.

The fugitive president is accused of being behind the deaths of more than 100 protesters at the hands of riot police.

Unrest in Ukraine began in November when Mr Yanukovych rejected a landmark association and trade deal with the EU in favour of closer ties with Russia.

Ukraine is close to bankruptcy and with promised loans from Russia looking increasingly unlikely, interim leaders are looking to the West to bail the country out.

EU foreign affairs chief Catherine Ashton held talks in Kiev on Tuesday to discuss financial and political support for Ukraine's new leaders.

She urged the provisional authorities to include Yanukovych supporters in any new government, adding: "Everyone I've spoken to here recognises the importance of this country sticking together. But we also know that there are big financial and economic challenges in the days, weeks and months ahead."

Yanukovych's flight from Kiev

21 Feb: leaves Kiev for Kharkiv on helicopter; stays overnight in state residence

22 Feb: flies by helicopter to Donetsk airport; tries to leave on private jet but stopped by border guards; leaves by car for Crimea

23 Feb: arrives in Balaklava, Crimea, and stays briefly in a private spa before making aborted attempt to reach Belbek airport

Dismisses most of his security detail; leaves Balaklava in a three-car convoy with some guards and presidential administration head Andriy Kliuyev